WATERMARKS

The Federal Reserve is scheduled to release a new $100 bill, the latest in a series of government efforts since 2003 to protect U.S. paper currency from counterfeiters by redesigning the denominations.

The new Benjamin's updated security features include an image of a luminescent, colour-shifting bell within a copper-coloured inkwell, and an embedded blue ‘security ribbon’ with optical properties that change images of bells to 100s and back again when the bill is tilted. Then there is the bill's portrait watermark of Benjamin Franklin himself, visible on the front and back.

In our ever-digitizing world, the remarkable, old-fashioned watermark holds its own. There it is, amid the flashy newfangled technology of the digital age-the QR codes, the patterned micro-perforations and the functional inks that interact with magnets, not to mention experimental currency systems like Bitcoin, which do away with paper entirely.

The first watermark that originated on paper was in the form of an ‘F’ and was produced by a mill in Cremona, in northern Italy; it dates to as early as 1271 and proved useful for identification and tracking purposes, suggesting its future role as a deterrent to forgery. The earliest English watermarks date to circa 1494. In the 1790s, English papermakers and mould makers who sympathized with loyalists during the French Revolution produced counterfeit paper with light and dark watermarks with the aim of ruining the currency of the Revolutionary government. Their efforts reportedly led to development of new techniques for making watermarks; for example, by the 1840s, English mills were producing some of the first three-dimensional watermarks.

The ‘water’ in the word derives from the traditional papermaking process, during which a pair of screens with a pressed mat of cellulosic fibres (extracted from anything from hemp to esparto grass) was suspended in water. Wire watermark forms of the same shape would be attached to the screens, or moulds. The watermark refers to the process and to the resulting design consolidated by hydrogen bonding within the intermingled fibres during a period of drainage and vacuum.

Historically the relationship between watermark quality and paper durability has been interwoven, literally and figuratively: good watermark quality has resulted from a short-fibered, well beaten stock (or slurry), as beating splits the long fibres. However, short fibres (or fibrils) make for a weaker paper. Our U.S. notes today are made of two cellulosic plant fibres, cotton and flax, and usually treated or infused with a coating to keep the paper clean and further increase its durableness-important because rumpled or soiled bills are easier to counterfeit.

Once governments and banks, not private firms, began to produce paper currency, watermarks took on new significance as a means of deterring counterfeiters. When the Governor and Company of the Bank of England was incorporated in July 1694, the debut of the world's first national currency marked a new era for the primacy of paper bank notes. After some were counterfeited in 1695, the Bank of England had to find a way to secure them. So beginning in 1697, the Sutton Courtenay Mill, in Berkshire south east England, manufactured watermarked paper with a loop pattern for the Bank's smaller denomination banknotes.

In 1724, the Bank transferred its contract to the mills of Henri Portal, to provide a steady supply of banknote paper with a more distinctive, and therefore more secure, watermark. The price for greater security was "eight shillings per rheam," as stated in the draft contract.

The making of watermark designs for fiduciary printing was a complicated process. Consider this description of a mould maker's handiwork in fashioning wire profiles to produce a design with wavy lines for the Bank of England's five pound banknotes, beginning in 1801:

"In a pair of five pound banknote moulds ... there were 8 curved borders, 16 figures, 168 large waves, and 240 letters, which had all to be separately secured by the finest wire to the waved surface. There were 1,056 wires, 67,584 twists, and the same repetition where the stout wires were introduced to support the under surface. Therefore, with the backing, laying, large waves, figures, letters and borders, before a pair of moulds was completed, there were some hundreds of thousands of stitches ..."

Even when security watermarks became easier to create, using the 1849 invention of a steel die to press out the wire profile with a steam hammer (thus doing away with wire stitching), the metallic plate yet required laborious hand-filing.

For both British and U.S. paper banknotes that contain watermarks, the watermarks are still produced traditionally, using a screen that places the watermark in the slurry before it sets.

Maybe watermarks will never be the talk of Silicon Valley or Silicon Alley, but they remain a genuinely useful security feature of U.S. and British paper currency. One way we know that is that professional counterfeiters are still trying to simulate them.